The present invention relates to a regulator for an alternator installed in a vehicle.
In a regulator for an alternator installed in a vehicle, it is known to control the voltage of the alternator based on a detected output voltage of a battery provided at the vehicle. An alternator disclosed in U.S. Pat. No. 3,852,653, a battery output voltage detection terminal S is connected to an alternator output voltage terminal B via a diode and a resistor which are serially connected. Voltage detection is switched to the alternator output voltage terminal B if a wire connecting the battery to the battery output voltage detection terminal S is disconnected from the battery. Similarly, voltage detection is switched to the battery output voltage detection terminal S if a wire connecting the battery to the alternator output voltage terminal B is disconnected from the battery. Such a regulator can adequately control an alternator installed at a vehicle, since the battery output voltage can be detected even if a wire connecting the battery to the battery output voltage detection terminal S is disconnected, or a wire connecting the battery to the alternator output voltage terminal B is disconnected.
However, in the above-mentioned conventional regulator, since a battery output voltage detection terminal S and an alternator output voltage terminal B are connected via a diode and a resistor, the following problem can occur: If the battery output voltage detection terminal S is irradiated by radio frequency noise from radio equipment, the battery output voltage detection terminal S and the diode (of which an anode is connected to the terminal S) detect a high-frequency carrier wave of the radio waves, and the voltage V0 at the cathode of the diode increases. Further, it is also likely that the alternator will stop generating power or that a charging state display lamp will be wrongly turned on, due to the increase of the voltage V0, notwithstanding that the battery 6 is not fully charged.